How do you stress a vowel-less word

If one were to feel the need to put extra emphasis on a preposition, how would you do it if the preposition were "с" or "в"?
In text people usually italicise the word, but what about speech.

Do it without talking! (raising voice, and more tense on italic word)

"Without it - you'll die, but with it - you'll prosper." (Would you pronounce this in Russian with a lengthened "С"?) ("with" and "without" in this case meaning "having" as opposed to "using", so not instrumental)

I want to say that you would use the vowel-added version со, but experience tells me that these version are strictly dependent on the following word.

Well... We really put something like vowel in this case after "с" and "в". I would name it "eaten 'ы'". It goes from the lowest levels of throat. While saying "s" you begin to say "ы", but end it before it becomes distinguishable "ы" vowel. Tongue and teeth are saying "s" but throat is saying "ы".
There is no dependence on the following word.
It's better to hear...